The proposed research addresses basic memory processes in orangutans (Pongo pygmaeus), gorillas (Gorilla gorilla gorilla) and rhesus monkeys (Macaca mulatta) using a modified Matching-to-Successive-Samples (MTSS) task analogous to free recall procedures in human subjects. The overall goal is to compare specifics of nonverbal serial memory empirically across individuals and species to identify similarities and differences in how nonhuman primates produce a serial list. The organizational strategies spontaneously developed by nonhuman primates as they acquire serial lists will be addressed first. A series of subsequent experiments will investigate encoding process in serial learning to determine (1) the extent to which nonhuman primates will use the order of list items to facilitate encoding, (2) whether subjects encode lists as a unitary whole, (3) short-term memory for item identity and order, (4) the extent to which categorical information facilitates encoding, and (5) whether experience with organizational schemes promotes organization of unrelated items. The results of the proposed research will provide basic information about nonverbal memory processes.